Antibody drug conjugates (ADC) are targeted chemotherapeutic molecules combining the properties of both antibodies and cytotoxic drugs by targeting potent cytotoxic drugs to antigen-expressing tumor cells, internalization, and release of drug, thereby enhancing their anti-tumor activity (Carter, P. and Senter, P. (2008) The Cancer Jour. 14(3):154-169). Successful ADC development for a given target antigen depends on optimization of antibody selection, linker design and stability, cytotoxic drug potency and mode of drug and linker conjugation to the antibody (Polakis, P. (2005) Current Opinion in Pharmacology 5:382-387).
The 5-amino-l-(chloromethyl)-1,2-dihydro-3H-benz[e]indole (amino CBI) class of DNA minor groove alkylators are potent cytotoxins (Atwell, et al (1999) J. Med. Chem., 42:3400), and have been utilized as effector units in a number of classes of prodrugs designed for cancer therapy. These have included antibody conjugates, (Jeffrey, et al. (2005) J. Med. Chem., 48:1344), prodrugs for gene therapy based on nitrobenzyl carbamates (Hay, et al (2003) J. Med. Chem. 46:2456) and the corresponding nitro-CBI derivatives as hypoxia-activated prodrugs (Tercel, et al (2011) Angew. Chem., Int. Ed., 50:2606-2609). The CBI and pyrrolo[2,1-c][1,4]benzodiazepine (PBD) pharmacophores have been linked together by an alkyl chain (Tercel et al (2003) J. Med. Chem 46:2132-2151). PBD dimers, where two pyrrolo[2,1-c][1,4]benzodiazepine units are tethered by an alkylene or alkylene-arylene chain are highly efficient interstrand crosslinking agents that react with guanine in the DNA minor groove (Rahman et al (2009) Jour. Amer. Chem. Soc. 131(38):13756-13766; Thurston et al (1994) Chem. Rev., 94:433-465; Bose et al (1992) J. Am. Chem. Soc. 114:4939-4941; Gregson et al (2004) Jour. Med. Chem. 47(5):1161-1174; U.S. Pat. Nos. 7,511,032; 7,528,1267,557,099; 7,049,311; 7,067,511; 7,265,105) and have activity against gram-positive bacteria (Doyle et al (2009) Jour. Antimicrob. Chemo. 65(5):949-959; Hadjivassileva et al (2005) Jour. Antimicrob. Chemo. 56(3):513-518), human B-cell chronic lymphocytic leukemia (CLL) cells (Pepper et al (2004) Cancer Res. 64(18):6750-6755), and solid tumors (Hochhauser et al (2009) Clin. Cancer Res. 15(6):2140-2147; Alley et al (2004) 64(18):6700-6706; Hartley et al (2004) Cancer Res. 64(18):6693-6699). Dimeric forms of PBD have been linked to antibodies to form ADC (US 2009/304710; US 2010/047257; US 2009/036431; WO 2011/130598, WO 2011/130616; US 2013/0028919).